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m pulsetrain. In the particular case when pulses are transmitted at the minimuminterval ri = l/2/i possible without intersymbol interference in the ab-sence of a low-frequency cut-off, the pulse train will ultimately vanishwhen an infinite seciuence of pulses of one polarity is transmitted, asillustrated for the last case in Fig. 33. The number of pulses of one polarity, or nearly all of the same po-larity, which can be transmitted before the limiting condition illustratedin Fig. 33 is approached depends on the extent of the low-frequencycut-off. If the low-frequency cut-off is inappreciable, this number maybe sufficiently great so that the probability of encountering such asequence in a random pulse train and resultant errors in reception maybe so small that it can be disregarded. The reciuirement of the low-frequency cut-off which is necessary to this end is evaluated below forpulses transmitted at intervals n = l/2/i. TRANSMISSION FREQUENCYCHARACTERISTIC WITHOUTLOW-FREQUENCY CUTOFF

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